The values of the normalized concentration in the occupied zone (Cn) in an office space arecalculated by CFD for five different ventilation systems and the minimum ventilation rate which maintains the average concentration in the occupied zone under the regulated value is analyzed. Energy consumptions associated with the change in ventilation rate are analyzed. In this analysis, for most ventilation systems, the value of Cn is around 1.0, but for large circulation flow ventilation systems it changes greatly depending on the supply inlet velocity and temperature.
The effects of exterior thermal transmission modeling for walls and a roof on the airconditioning heat load prediction for a large space building were analyzed using a coupled simulation of convection based on CFD, radiation and conduction. Three cases were simulated: first, a simplified model using sol-air temperature (SAT) as outdoor boundary conditions; second, a rigorous model where both outdoor and indoor spaces were calculated simultaneously; and, third, using sol-air temperature modified by the results of the second case.
In this paper a method to solve a design problem of hybrid ventilation system is proposedby building stack pressure around the ventilator using a flat bed, glass-shielded rectangular solarchannel. In support of this idea a CFD (Computational Fluid Dynamics) simulation based ontheoretical calculation is done. Here, natural convection and a k-e two-equation turbulence modelwere used together with the finite volume method.
The development of a new device for the injection of tracer gas is discussed with the objective of practical application in the field of HVAC airflow measurements. The uniform tracer gas dispersion for very short distances, when measuring airflow by the constant emission method is of great interest. This new injection device has a compact tubular shape, with magnetic fixation to be easy to apply to duct walls. After a preliminary study with an initial prototype already tested, further detailed experiments had been carried out, culminating in a second prototype.
Using computational fluid dynamics (CFD) techniques to model buoyancy-driven airflows hasalways proved challenging. This work investigates CFD modelling of buoyancy-driven natural ventilation flows in a single-storey space connected to an atrium. The atrium is taller than the ventilated space and when warmed by internal heat gains producing a column of warm air in the atrium and connect space drives a ventilation flow. Results of CFD simulations are compared with predictions of an analytical model and small-scale experiments .
The main goal of this work is the modeling of the flow field and temperature distribution in thekitchen of a house where natural ventilation techniques were implemented. The Fluent 6.1 commercial CFD software was used. The k- e turbulence model and the Boussinesq approximation for buoyancy were employed. The heat released from a water heater in continuous operation dictates the temperature distribution in the kitchen. Several simulations were performed by varying the boundary conditions and seeking agreement with the available experimental data.
In order to clarify whether a combination of designs is optimal, design elements are divided intodesign variables and random variables in the inquiry process for the optimal design. Design variablesrelated to the model are selected by a genetic algorithm, and random variables related to outdoor condition are selected by the moment method. The whole process of optimization consisted of a two-step procedure to reduce the calculation loads for finding the optimal solution. This study carried out a simple analysis using a coarse mesh considering the calculation loads in the first step.
Wind-driven cross-ventilation in a single-zone cubic building with two large openings is investigated using a computational fluid dynamics approach. We analyzed the driving force and the ventilation flow rate due to wind as a function of the relative location and geometry of the two ventilation openings. The aim is to understand how well the conventional simple macroscopic method predicts the ventilation flow rate and when the simple method fails. Parametric studies were completed using building envelope porosity as the primary variable of interest.
This paper investigates the single-sided natural ventilation through a VELUX centre pivot roof window under natural weather conditions. The aim of the investigation is to develop an empirical formulation for air flow rate through a roof window based on CFD and tracer gas decay measurement methods. CFD can separate buoyancy and wind effects in the calculation of the air flow rate through a window opening, but it is difficult to isolate wind effect from buoyancy forces during measurements.